The retinal pigment epithelium (RPE) is vital to the normal structure and function of the sensory retina. Disorders of the RPE are directly or indirectly responsible for many debilitating visual problems in man, including senile macular degeneration (SMD). The basement membrane of the RPE constitutes a significant portion of Bruch's membrane where abnormalities such as thickening, breaks, etc. are commonly found in macular diseases such as drusen, angioid streaks, and SMD. The RPE produces its own collagenous basement membrane normally and damage or disease may result in "fibrous metaplasia" of the RPE with production of possibly altered collagen and fibrous material by such cells. The objectives of this study are to evaluate the role of collagen synthesis and basement membrane production of the RPE and to compare these "normal" epithelial cells with RPE cells which have been stimulated to fibrous metaplasia. Rabbit RPE cells will be established and cultured through techniques available in our laboratories. Biosynthesis of collagen by RPE in culture will be studied employing techniques currently utilized by the Connective Tissue Laboratories directed by one of us (Nimni). Fractionization of collagen chains by SDS-polyacrylamide gel electrophoresis with 5% gels, carrier-free carboxymethylcellulose chromatography (CMC), or gel filtration chromatography will be performed. Collagen type will be determined by cyanogen bromide peptide mapping. Fibroblastic metaplasia of RPE cells will be induced by photic stimulation and/or cryotherapy, producing a fibrous membrane. The diseased cells will be investigated by electron microscopy as well as routine histopathology for ultrastructural and morphological correlations. Collagen formed as a result of fibrous metaplasia will be studied with the hope of providing added insight into the pathogenesis of defects at the level of the RPE and Bruch's membrane.